Typical gas lift equipment comprised a side pocket mandrel having a pocket sub welded into a window in the mandrel near the lower end thereof. The sub has upper and lower polish bores in which spaced-apart packing elements on the gas lift valve are seated. Gas entry ports are provided through the outer wall of the sub between the polish bores, and the valve has an outlet flow port through its nose through which the gas passes into the interior of the mandrel in the region below the lower polish bore. An inwardly directed latch shoulder that is located above the upper polish bore cooperates with a latch on the upper end of the valve to releasably retain the valve in the pocket. A structure of this general type is shown in U.S. Pat. No. 3,827,490, issued Aug. 6, 1974.
Our U.S. patent application Ser. No. 789,313, filed, Oct. 18, 1985, illustrates and claims a new and improved side pocket mandrel having a short-length seating sub welded to the upper end of the main body section of the mandrel. The seating sub has a single polish bore that leads to the outside of the mandrel along an axis that is inclined at a small angle with respect to the axis of the main bore of the mandrel. A latch shoulder located near the inner end of the polish bore is arranged to cooperate with a latch element on the gas lift valve in order to releasably hold the valve in a position where its packing assembly sealingly engages the polish bore. The body of the valve extends out into the tubing-casing annulus, and has one or more inlet ports in the wall thereof. A gas outlet port is provided in a special section of the valve that is connected between the packing assembly and the latch assembly.
If the direction of the gas outlet passage is not properly oriented with respect to the main bore of the mandrel, high velocity gas flow over a period of time could conceivably erode inner wall surfaces of the seating sub, and result in mandrel failure should the damage becomes significant. Of course a special surfacing material could be used to inhibit damage, much in the nature of a "blast joint", however this could increase the manufacturing cost of the mandrel in an undesirable manner.
It is the general object of the present invention to provide a gas lift valve and seat sub assembly of the type described that are constructed in a manner such that when the valve is seated, the outlet gas flow port is oriented in a direction such that flow is always toward the main bore of the mandrel through which production fluid is passing.